1. Field of the Invention
This invention relates to a polymeric tertiary amine stabilizer for polyurethane polymer. More particularly, the invention concerns an improvement in such a stabilizer to make it especially suited for use with polyurethane/urea spandex fibers and films.
2. Description of the Prior Art
Hunt, U.S. Pat. No. 3,428,711, suggests use of polymeric tertiary-aminoalkyl acrylates and methacrylates for stabilizing segmented polyurethanes. A preferred stabilizer of Hunt, which has found much commercial use in spandex fibers is a copolymer of sterically hindered diisopropylaminoethyl methacrylate (hereinafter referred to as "DIPAM") and n-decyl methacrylate (hereinafter "DM"). The copolymer (hereinafter "poly(DIPAM/DM)") provides spandex polymer with greater resistance to degradation upon exposure o chlorine than similar amines which are not sterically hindered.
Although the known polymeric hindered tertiary amine additives are useful in preventing degradation and discoloration of spandex polymers, these additives also can cause manufacturing problems and/or poor properties in fibers made from the spandex polymer. For example, use of poly(DIPAM/DM) additive has been found to cause certain problems in the dry-spinning of filaments from spandex polymer solutions. Dimethylacetamide (hereinafter "DMAc") is the most frequently used solvent for preparing the spandex polymer solutions. The poly(DIPAM/DM) and other additives, such as antioxidants and pigments, are usually formed into a slurry with DMAc and then mixed with spandex polymer solution prior to spinning. However, such slurries, which usually are prepared at room temperature, can undergo phase separation when the polymeric amine lacks solubility in the DMAc solvent. Phase separation can lead to agglomeration of the additive, problems in spinning and/or nonuniform distribution of the additives in the spinning solution and in the filaments spun therefrom. Use of poly(DIPAM) homopolymer, which is quite soluble in DMAc, causes an undesired reduction in elasticity (i.e., set) of the dry-spun spandex filaments.
It is an object of the present invention to provide in a spandex polymer, a polymeric, hindered tertiary amine additive that protects the spandex polymer against degradation and discoloration and avoids, or at least significantly reduces, the above-described problems related to use of the known polymeric, hindered tertiary amines.